Cylindrical tube formation

ABSTRACT

Tube forming methods can be used for efficient transition in the production of tubes having varying thickness. Material used to form consecutive tubes may have the same thickness along a separation plane separating a first discrete section from a second discrete section of the material, and the first discrete section and the second discrete section may each have varying thickness in a feed direction of the material. With such a thickness profile, the first discrete section of the material may be formed into a first cylinder having varying thickness and separated from the second discrete portion as the second discrete section is formed into a second cylinder having varying thickness. In particular, the transition between the first cylinder and the second cylinder may be achieved without scrap and/or interruption, resulting in cost-savings and improvements in production throughput associated with forming tubes having varying thickness.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.15/870,612, filed Jan. 12, 2018, which claims the benefit of U.S.Provisional Patent Application No. 62/445,520, filed on Jan. 12, 2017,with the entire contents of each of these applications herebyincorporated herein by reference.

BACKGROUND

Tubes are ubiquitous in industrial applications, with some common usesincluding supporting wind turbines (or other machinery) and transportingfluid. It is often desirable to vary thickness of one or more tubesformed for a particular application. For example, in large-scaleindustrial applications, such as formation of wind turbine towers, tubesused to form such towers are built in a factory setting and are limitedto a maximum diameter constrained by transportation restrictions. Withdiameter of the tube constrained in this way, it is often desirable tovary wall thickness of the tube along the length of the tube to form thetube with desired structural performance characteristics. In particular,it is often desirable for the wall thickness to gradually increase alongone direction in the tube (e.g., to accommodate the increasing momentloading along the axis of the tube, so that the thickness at one end ofthe tube is substantially greater than the thickness at the other end ofthe tube).

Variation of thickness of tubes, however, creates certain challengeswith respect to efficient use of material and throughput in productionprocesses used to form these tubes. As an example, transitions inthickness from one tube to the next may produce scrap, for example, whenthe change in thickness is too large to be accommodated by a continuousproduction process. This may occur, for example, at the transitionbetween two instances of the same tube with gradually increasing wallthickness, with the first end having a substantially greater thicknessthan the second end. Further, if the tube is being formed using acontinuous production process, the process may need to pause for thethickness change to be accommodated. For example, before the next tubecan be formed, the scrap must be removed and additional steps taken tore-start the process. Production of scrap and slowing or pausing thecontinuous production process can both add significantly to the cost ofa tube. Thus, there remains a need for improved methods of producingtubes having longitudinal variations in thickness.

SUMMARY

Tube forming methods can be used for efficient transition in theproduction of tubes having varying thickness. Material used to formconsecutive tubes may have the same thickness along a separation planeseparating a first discrete section from a second discrete section ofthe material, and the first discrete section and the second discretesection may each have varying thickness in a feed direction of thematerial. With such a thickness profile, the first discrete section ofthe material may be formed into a first cylinder having varyingthickness and separated from the second discrete section as the seconddiscrete section is formed into a second cylinder having varyingthickness. In particular, the transition between the first cylinder andthe second cylinder may be achieved without scrap and/or interruption,resulting in cost-savings and improvements in production throughputassociated with forming tubes having varying thickness.

According to one aspect, a method of forming a tube may include moving amaterial in a feed direction into a curving device, the material havinga first discrete section abutting a second discrete section along aseparation plane intersecting the material, the first discrete sectionand the second discrete section having the same thickness at theseparation plane and each having a varying thickness in the feeddirection, as the material intersected by the separation plane movesthrough the curving device, forming the material into a first cylinderhaving a spiral seam intersected by the separation plane, joining thefirst discrete section to itself and to the second discrete sectionalong the spiral seam, and severing the first discrete section from thesecond discrete section along the separation plane intersecting thespiral seam along a position at which the first discrete section isjoined to the second discrete section.

In certain implementations, the material may be continuously moved inthe feed direction.

In some implementations, forming the material into the first cylindermay include bending a first edge of the first discrete section adjacentto a second edge of the second discrete section at the intersection ofthe separation plane and the spiral seam.

In certain implementations, the separation plane may be perpendicular toa longitudinal axis defined by the first cylinder.

In some implementations, the material may include a plurality of sheetssecured to one another in a direction intersecting the feed direction.For example, the separation plane may substantially bisect one sheet ofthe plurality of sheets. In certain instances, the substantiallybisected sheet may be longer than at least one adjacent sheet in theplurality of sheets. Further, or instead, joining the first discretesection to itself and to the second discrete section may include formingcorner seams of the material along the spiral seam. The separation planemay intersect the spiral seam along a portion of the spiral seam spacedapart from the corner seams.

In certain implementations, the first discrete section may be severedfrom the second discrete section as a segment of the second discretesection is in the curving device.

In some implementations, the method may further include forming thesecond discrete section into the second cylinder. For example, a leadingedge of the second cylinder may be bounded by the separation plane alongwhich the first discrete section is severed from the second discretesection.

In certain implementations, at least a portion of the first discretesection may have a monotonically changing thickness along the feeddirection, and at least a portion of the second discrete section mayhave a monotonically changing thickness along the feed direction. Thethickness of one of the at least one portion of the first discretesection and the at least one portion of the second discrete section mayincrease in the feed direction, and the thickness of the other one ofthe at least one portion of the first discrete section and the at leastone portion of the second discrete may decrease in the feed direction.Further or instead, a variation in the thickness of the first discretesection may be symmetrically mirrored by a variation in the thickness ofthe second discrete section about the separation plane.

In some implementations, the material moved into the curving device is aplanar strip of metal. Further or instead, the curving device mayinclude a plurality of roll banks arranged as a triple roll.

In certain implementations, joining the first discrete section to itselfand to the second discrete section along the spiral seam may includecontinuously welding the material.

In some implementations, severing the first discrete section from thesecond discrete section may include cutting along an entirecircumference of the first cylinder.

In certain implementations the first cylinder may be undeformed as thefirst discrete section is severed from the second discrete section.

Other aspects, features, and advantages will be apparent from thedescription and drawings, and from the claims.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a side view of a cylindrical tube having a longitudinalvariation in thickness.

FIG. 2 is a schematic representation of a production order for formingthe cylindrical tube of FIG. 1 in a continuous production process.

FIG. 3 is a top view of sheets of a material arranged in a sequencebased on the production order of FIG. 2.

FIG. 4 is a block diagram of a fabrication system.

FIG. 5 is a schematic representation of a spiral forming process carriedout by the fabrication system of FIG. 5 on the sheets of material inFIG. 3 to form the cylindrical tube of FIG. 1 in a continuous productionprocess.

FIG. 6 is a flowchart of an exemplary method of forming a tube.

FIG. 7 is a side view of cylindrical tubes of varying dimensions, witheach cylindrical tube having a respective longitudinal variation inthickness.

FIG. 8 is a schematic representation of a production order for formingthe cylindrical tubes of FIG. 7 in a continuous production process.

Like reference symbols in the various drawings indicate like elements.

DETAILED DESCRIPTION

Embodiments will now be described more fully hereinafter with referenceto the accompanying figures. The foregoing may, however, be embodied inmany different forms and should not be construed as limited to theillustrated embodiments set forth herein.

All documents mentioned herein are hereby incorporated by reference intheir entirety. References to items in the singular should be understoodto include items in the plural, and vice versa, unless explicitly statedotherwise or clear from the context. Grammatical conjunctions areintended to express any and all disjunctive and conjunctive combinationsof conjoined clauses, sentences, words, and the like, unless otherwisestated or clear from the context. Thus, the term “or” should generallybe understood to mean “and/or” and, similarly, the term “and” shouldgenerally be understood to mean “and/or.”

Recitation of ranges of values herein are not intended to be limiting,referring instead individually to any and all values falling within therange, unless otherwise indicated herein, and each separate value withinsuch a range is incorporated into the specification as if it wereindividually recited herein. The words “about,” “approximately,”“substantially” or the like, when accompanying a numerical value, are tobe construed as including any deviation as would be appreciated by oneof ordinary skill in the art to operate satisfactorily for an intendedpurpose. Ranges of values and/or numeric values are provided herein asexamples only, and do not constitute a limitation on the scope of thedescribed embodiments. The use of any and all examples or exemplarylanguage (“e.g.,” “such as,” or the like) provided herein, is intendedmerely to better illuminate the embodiments and does not pose alimitation on the scope of the embodiments or the claims. No language inthe specification should be construed as indicating any unclaimedelement as essential to the practice of the disclosed embodiments.

In the following description, it is understood that terms such as“first,” “second,” “top,” “bottom,” “above,” “below,” “up,” “down,” andthe like, to the extent used herein, are words of convenience and arenot to be construed as limiting terms unless specifically stated.

Forming processes of the present disclosure are described with respectto formation of tubes useful for any one or more of a variety ofindustrial applications. For example, the tubes formed herein may bemounted with flanges and coupled to one another and, optionally, toother types of tubes to form a continuous hollow structure, such as maybe useful for forming at least a portion of wind towers, pilings, otherstructural pieces for civil engineers (e.g., columns), pipelines,ducting, and the like. Thus, as a more specific example and unlessotherwise specified or made clear from the context, the tubes formedaccording to the devices, systems, and methods described herein shouldbe understood to be useful as sections of towers used to support windturbines or other similar machinery. However, this is by way of exampleand should not be understood to limit the present disclosure in any way.

As used herein, the terms tube and cylinder shall be usedinterchangeably, unless otherwise specified or made clear from thecontext. More specifically, in the context of the present disclosure,tube and cylinder shall be understood to include a shape that issubstantially a right circular cylinder, allowing for dimensionalvariations in accordance with dimensional tolerances of the structurebeing formed. Further, or instead, tubes and cylinders of the presentdisclosure shall be understood to be hollow along a longitudinal axis ofthe substantially right circular cylinder shape.

Further, as used herein, the term thickness shall refer to wallthickness of a sheet of material in planar form or in a curved form, asthe case may be, according to the context. In a tube or cylinder thathas been formed or is in the process of being formed, then, thicknessshall be understood to be a radial dimension of material of therespective tube or cylinder at a given longitudinal position along thetube or cylinder. Thus, for example, a tube or cylinder having alongitudinal variation in thickness shall be understood to have a wallthickness that varies at least in a longitudinal direction along thetube or cylinder.

Referring to FIG. 1, a cylinder 100 having a length “L” and a diameter“D” may be formed of sheets t1, t2, t3, t4, t5, t6. Each sheet t1, t2,t3, t4, t5, t6 may have a respective thickness (e.g., a substantiallyuniform thickness). The respective thickness of at least one of thesheets t1, t2, t3, t4, t5, t6 may be different from the respectivethickness of at least another one of the sheets t1, t2, t3, t4, t5, t6such that, collectively, the sheets t1, t2, t3, t4, t5, t6 impart avariation in thickness along a longitudinal axis “C” defined by thecylinder 100. That is, in a longitudinal direction from t1 to t6,thickness of the cylinder 100 may vary according to any one or morepatterns and along all or a portion of the length “L” of the cylinder100. Thus, for example, the cylinder 100 may have a monotonicallyincreasing or decreasing thickness along at least a portion of thelength “L” of the cylinder 100 in a direction from t1 to t6. Variationin thickness of the cylinder 100 may be useful for achieving, forexample, target structural performance characteristics for the cylinder100 dimensionally constrained to a specific value or range of values ofthe diameter “D.” Further, or instead, as compared to forming thecylinder 100 with a material of uniform thickness selected based onmeeting the most stringent structural requirement along a portion of thecylinder 100 and over-dimensioned for structural requirements alongother portions of the cylinder 100, forming the cylinder 100 with avariation in thickness along the sheets t1, t2, t3, t4, t5, t6 may havesignificant advantages with respect to weight and cost savings. Stillfurther, or instead, and as described in greater detail below, thecylinder 100 may be formed according to one or more processes that mayfacilitate achieving additional efficiency in the use of material (e.g.,cost savings) and, in certain instances, increases in throughput of afabrication system used to form the cylinder 100.

Referring now to FIG. 2, a production order “P” represents formation ofmultiple instances of the cylinder 100 in sequence over time(represented by the direction of the arrow of the production order “P”)as the sheets t1, t2, t3, t4, t5, t6 are moved through a fabricationsystem in series. In FIG. 2, for the sake of explanation, the multipleinstances of the cylinder 100 produced in the production order “P” areshown as a continuous cylinder, such as would be formed by a fabricationsystem if the multiple instances of the cylinder 100 were not separatedfrom one another during the course of a fabrication process. Asdescribed in greater detail below, however, each instance of thecylinder 100 may be severed at a separation plane 200 to separate theinstance of the cylinder 100 from the next instance of the cylinder 100(e.g., as the next instance of the cylinder 100 is being formed) or toseparate the instance of the cylinder 100 from scrap 203 at thebeginning and end of the production order.

In general, the production order “P” may be based on arranging thevariations in thickness of the multiple instances of the cylinder 100relative to one another in a manner that produces little or no scrapduring transitions in the formation of each instance of the cylinder100. For example, in the production order “P,” the sheets t1, t2, t3,t4, t5, t6 may be arranged to form an alternating pattern having a firstdiscrete section 201 and a second discrete section 202 separated by theseparation plane 200. Thickness of the material of the first discretesection 201 may match thickness of the material of the second discretesection 202 at the separation plane 200, and thickness of each of thefirst discrete section 201 and the second discrete section 202 may varyin a direction away from the separation plane. For example, thevariation of the thickness of the first discrete section 201 in adirection away from the separation plane 200 may have mirror symmetrywith the variation of the thickness of the second discrete section 202in a direction away from the separation plane 200. As should begenerally understood, such symmetry may be particularly useful forforming substantially identical instances of the cylinder 100. However,as described in greater detail below, other variations in thickness ofthe first discrete section 201 with respect to variations in thicknessof the second discrete section 202 are additionally or alternativelypossible. To ensure that thickness of the first discrete section 201substantially matches the thickness of the second discrete section 202at the separation plane 200, the separation plane 200 may be positionedto extend through (e.g., to bisect) a single one of the sheets t1, t2,t3, t4, t5, t6 having a substantially uniform thickness.

According to the production order “P,” the first discrete section 201may be formed into a first instance of the cylinder 100 and severed fromthe second discrete section 202 along the separation plane 200 as thesecond discrete section 202 is moved through a fabrication system toform a second instance of the cylinder 100. Similarly, the seconddiscrete section may be formed into the second instance of the cylinder100 and severed from a next instance of the first discrete section 201along the separation plane 200 as the next instance of the firstdiscrete section 201 is moved through a fabrication system. In general,this alternating process may be repeated as necessary to form multipleinstances of the cylinder 100.

At each transition between instances of the cylinder 100, the firstdiscrete section 201 and the second discrete section 202 may match oneanother at the separation plane 200 according three criteria useful forreducing or eliminating scrap associated with transitions betweeninstances of the cylinder 100: 1) the first discrete section 201 and thesecond discrete section 202 may have matching taper at the separationplane 200; 2) the first discrete section 201 and the second discretesection 202 may have the same radius of curvature at the separationplane 200; and 3) the sheets t1, t2, t3, t4, t5, t6 may be arranged suchthat a thickness of the first discrete section 201 matches a thicknessof the second discrete section 202 along the separation plane 200. Thefirst two criteria are, in general, an artifact associated with formingmultiple instances of the cylinder 100, with each instance beingsubstantially similar to each other instance. The third criterion isfacilitated by the production order “P.”

In certain implementations, the production order “P” for formingmultiple instances of the cylinder 100 may be carried out continuously.That is, because scrap is not produced between formation of instances ofthe cylinder 100, it is unnecessary to stop the production process toremove scrap between instances of the cylinder 100. Rather, scrap 203 isproduced at the beginning and at the end of the production order “P,”when the impact of the scrap production on continuity of the productionorder “P” is not significant. Accordingly, as compared to a productionorder requiring periodic removal of scrap, the production order “P” maybe useful for improving throughput of fabrication of the cylinder 100and for reducing labor requirements.

Referring now to FIGS. 2 and 3, the production order “P” may form abasis for ordering the planar forms of the sheets t1, t2, t3, t4, t5, t6for feeding into a fabrication system. That is, conceptually, thecontinuous cylinder representing the production order “P” of multipleinstances of the cylinder 100 may be unwrapped to provide an orderingfor arranging the sheets t1, t2, t3, t4, t5, t6 as a material 300 to bemoved in a feed direction “F” into a fabrication system. As described ingreater detail below, in the fabrication system, the material 300 formedby the sheets t1, t2, t3, t4, t5, t6 may be curved and joined to forminstances of the cylinder 100, and each instance of the cylinder 100 maybe severed along a respective instance of the separation plane 200.

In general, the sheets t1, t2, t3, t4, t5, t6 may be formed of any oneor more materials suitable for withstanding load associated with aparticular application and formable into the cylinder (100) according toany one or more of the methods described herein. For the sake of clearexplanation, unless otherwise specified or made clear from the context,it should be generally understood that the sheets t1, t2, t3, t4, t5 t6are formed of the same base material such that any differences instructural performance of the sheets t1, t2, t3, t4, t5, t6 in a giveninstance of the cylinder 100 (FIG. 1) may be attributable to structuralcharacteristics of the sheets t1, t2, t3, t4, t5, t6. In particular,differences in structural characteristics of the sheets t1, t2, t3, t4,t5, t6 should be generally understood as being attributable todifferences in thicknesses of the sheets t1, t2, t3, t4, t5, t6. Itshould be more generally understood, however, that the sheets t1, t2,t3, t4, t5, t6 may have different material compositions in someimplementations.

The material 300 may be formed from the sheets t1, t2, t3, t4, t5, t6by, for example, joining the sheets t1, t2, t3, t4, t5, t6 in anend-to-end abutting relationship along cross-seams 301. The cross-seams301 may be formed according to any one or more of various differentjoining techniques suitable for the base material of the sheets t1, t2,t3, t4, t5, t6. For example, the sheets t1, t2, t3, t4, t5, t6 may eachbe each formed of steel (or another similar metal suitable forwithstanding loads associated with industrial applications and bendableto form the cylinder) and the cross-seams 301 may be formed according toany one or more of the welding techniques described herein.

In certain implementations, the separation planes 200 may be positionedrelative to the cross-seams 301 such that the separation planes 200 arespaced apart from the cross-seams 301. Such spacing may be useful, forexample, for reducing the likelihood of severing the material 300 alongcorner seams (such as a corner seam 501 in FIG. 5) formed at theintersection of the cross-seams 301 and a spiral along which thematerial 300 is curved to form the cylinder 100. Severing the material300 at or near the corner seams may create a geometry at which manyseams come together at once (e.g., the corner seam plus a seam joiningthe flange at the cut) and/or a geometry with fatigue properties thatare not fully represented in design codes.

As an example of spacing that may be useful for reducing the likelihoodof severing corner seams in the cylinder 100, the sheets t1, t2, t3, t4,t5, t6 may be collectively dimensioned such that each of the separationplanes 200 extends through a longer sheet that may be joined to itselfover a longer distance. As shown in FIG. 3, for example, t1 and t6 maybe longer than the other sheets such that the separation planes 200extending through those sheets may be suitably spaced apart from therespective cross-seams 301 and, thus, spaced apart from the corner seamsformed by the cross-seams 301.

The geometric criteria for the longer sheet is that its length must begreater than:

L≥√{square root over ((πD)² +ŝ2)}

where L is the length of sheet, D is the diameter of the cylindricalsection, and s is the width of the sheet.

Referring now to FIGS. 3-5, a fabrication system 400 may include a stocksource 404, a feed system 406, a curving device 408, a joining system410, a severing system 412, and a control system 414. As described ingreater detail below, the fabrication system 400 may be operable tofabricate multiple instances of the cylinder 100 (FIG. 1) according tothe methods described herein. The control system 414 may control each ofthe stock source 404, the feed system 406, the curving device 408, thejoining system 410, and the severing system 412. In someimplementations, the control system 414 may control more or fewercomponents of the fabrication system 400, and any combinations thereof.For example, the control system 414 may additionally control a runoutsystem to move instances of the cylinder 100 in a direction away fromthe curving device 408 and/or the joining system 410.

The control system 414 may include a processing unit 420 and a storagemedium 440 in communication with the processing unit 420. The processingunit 420 may include one or more processors, and the storage medium 440may store computer-executable instructions that, when executed by theprocessing unit 420, cause the fabrication system 400 to perform one ormore of the tube forming methods described herein. Optionally, thecontrol system 414 may include an input device (e.g., a keyboard, amouse, and/or a graphical user interface) in communication with theprocessing unit 420 and the storage medium 440 such that the processingunit 420 is additionally, or alternatively, responsive to input receivedthrough the input device as the processing unit 420 executes one or moreof the tube forming methods described herein.

More generally, the control system 414 may include any processingcircuitry configured to control operation of the fabrication system 400.This may, for example, include dedicated circuitry configured to executeprocessing logic as desired or required, or this may include amicrocontroller, a proportional-integral-derivative controller, or anyother programmable process controller. This may also or instead includea general-purpose microprocessor, memory, and related processingcircuitry configured by computer executable code to perform the variouscontrol steps and operations contemplated herein.

More generally, the controller 28 may include any processing circuitryconfigured to receive sensor signals and responsively control operationof the fabrication system 20. This can, for example, include dedicatedcircuitry operable to execute processing logic as desired or required,or this can include a microcontroller, aproportional-integral-derivative controller, or any other programmableprocessor controller.

The stock source 404 may include the sheets t1, t2, t3, t4, t5, t6,which may be stored in a magazine or other suitable dispenser tofacilitate selection and loading of the sheets t1, t2, t3, t4, t5, t6during manufacturing.

Between the stock source 404 and the feed system 406, the sheets t1, t2,t3, t4, t5, t6 may be joined (e.g., welded) to one another at thecross-seams 301 to form the material 300. In general, the cross-seams301 may be oblique to the feed direction “F” along which the material300 is moved into the curving device 408. More specifically, thecross-seams 301 may be perpendicular to the feed direction “F” alongwhich the material 300 is moved into the curving device 408.

The feed system 406 may be operable to transport the material 300 fromthe stock source 404 to and/or through the curving device 408. The feedsystem 406 may include, for example, one or more pairs of drive rollspinching the material 300 such that rotation of the drive rolls can movethe material 300 in the feed direction “F.” More generally, anyequipment suitable for moving planar material according to any ofvarious different techniques known in the art may be used to move theplanar form of the material 300 from the stock source 404 to, and in insome instances through, the curving device 408. Such equipment mayinclude, for example, robotic arms, pistons, servo motors, screws,actuators, rollers, drivers, electromagnets, or combinations thereof. Incertain implementations, the feed direction “F” may be substantiallyconstant (e.g., with the one or more pairs of drive rolls of the feedsystem 406 in a substantially stationary position as the one or morepairs of drive rolls move the material 300 to and through the curvingdevice 408).

The curving device 408 may impart a controllable degree of curvature tothe material 300 fed into it. The curving device 408 may include, forexample, a roll bender 502 including roll banks positioned relative toone another and to the material 300 to impart curvature to the material300 fed through the roll bender 502. In certain instances, the rollbanks of the roll bender 502 may be arranged as a triple-roll and,further or instead, the roll banks may be movable relative to oneanother to vary a bending moment applied to the material 300 movingthrough the roll bender 502. Such a variation in the bending moment maybe useful, for example, for bending the sheets of variable thickness(e.g., the sheets t1, t2, t3, t4, t5, t6) to the same diameter to formthe cylinder 100 (FIG. 1).

In general, the curving device 408 may impart a bending moment to aplanar form of the material 300. More specifically, the curving device408 may impart a bending moment to the material 300 along the firstdiscrete section 201 and the second discrete section 202 as the material300 moves through the curving device 408. Thus, for example, as aportion of the material 300 intersected by the separation plane 200moves through the curving device 408, the material 300 may be formedinto a first cylinder 504 having a spiral seam 503 intersected by theseparation plane 200. As a more specific example, the curving device 408may form the material 300 having the spiral seam 503 by bending thematerial 300 such that a first edge of the first discrete section 201 isadjacent to a second edge of the second discrete section 202 at theintersection of the separation plane 200 and the spiral seam 503.Through processing (e.g., joining and severing) described in greaterdetail below, the first cylinder 504 may be formed into an instance ofthe cylinder 100 (FIG. 1).

The joining system 410 may mechanically couple the material 300 toitself along the spiral seam 503. For example, the first discretesection 201 and the second discrete section 202 may be oriented relativeto one another such that the joining system 410 may join the firstdiscrete section 201 to itself and to the second discrete section 202along the spiral seam 503 (e.g., at the intersection of the separationplane 200 and the spiral seam 503). Continuing with this example, withthe first discrete section 201 joined to itself and to the seconddiscrete section 202 (at least at the intersection of the separationplane 200 and the spiral seam 503), the first discrete section 201 andthe second discrete section 202 may have sufficient mechanical strengthalong the separation plane 200 to withstand a severing process,described in greater detail below, for separating the first cylinder 504from the second discrete portion 202 as the second discrete section 202moves through the curving device 408.

The joining system 410 may include, for example, one or more weld heads508 suitable for welding the material 300 to itself along the spiralseam 503 as the material 300 moves through the curving device 408. Ingeneral, the one or more weld heads 508 may be positioned to weld thematerial 300 along an inside surface and/or along an outside surface ofthe material 300 in a curved state to hold the material 300 togetheralong the spiral seam 503. A variety of techniques for welding are knownin the art and may be adapted for joining the sheets t1, t2, t3, t4, t5,t6 together to form the material 300 and for joining one or more edgesof the material together as contemplated herein. This can, for example,include any welding technique that melts a base metal or other materialalong the spiral seam 503, optionally along with a filler materialadapted to the joint to improve the strength of the bond. Conventionalwelding techniques suitable for structurally joining metal include, byway of example and not limitation: gas metal arc welding (GMAW),including metal inert gas (MIG) and/or metal active gas (MAG); submergedarc welding (SAW); laser welding; and gas tungsten arc welding (alsoknown as tungsten, inert gas or “TIG” welding); and many others. Theseand any other techniques suitable for forming a structural bond betweenedges of the material 300 may be adapted for the joining system 410 and,more generally, for any manner and form of joining described herein. Themechanical coupling imparted by the joining system 410 may be, forexample, continuous along the spiral seam 503 to provide enhancedstructural strength to the first cylinder 504 and, ultimately, toinstances of the cylinder 100 (FIG. 1). The mechanical coupling may alsoor instead include intermittent coupling (e.g., at fixed distances)along the spiral seam 503 to facilitate, for example, faster throughputfor applications in which structural strength of the cylinder 100(FIG. 1) is not a key design consideration.

The severing system 412 may, in general, mechanically separate the firstdiscrete section 201 and the second discrete section 202 from oneanother along the separation plane 200 to form instances of the cylinder100 (FIG. 1). Specifically, with reference to the example shown in FIG.5, the severing system 412 may separate the first discrete section 201(in the form of the first cylinder 504) from the second discrete section202 as the second discrete section 202 is moving through the curvingdevice 408 and being formed into a second cylinder 505. In certainimplementations, the severing system 412 may achieve such separationwith little or no deformation of the first discrete section 201 and thesecond discrete section 202.

The severing system 412 may include, for example, a cutting head 506 anda track 507. The cutting head 506 may be, for example, any of variousdifferent known torch cutting methods known in the art as being usefulfor cutting metal and, in particular, steel. Thus, for example, thecutting head 506 may be a plasma cutting torch and/or an oxy/acetyleneflame cutting torch. Additionally, or alternatively, the cutting head506 may include a mechanical separation device, such as a metal-cuttingsaw.

The cutting head 506 may travel on the track 507 for appropriatepositioning. For the sake of clarity of illustration, the cutting head506 in FIG. 5 is shown in an inactive state, away from the separationplane 200. In use, the cutting head 506 may be moved along the track 507to maintain alignment with the separation plane 200 as the material 300moves through the curving device as the second cylinder 505 continues tobe formed from the second discrete section 202 of the material 300. Withthe cutting head 506 aligned with the separation plane 200, the cuttinghead 506 may cut the material 300 along the separation plane 200 as thefirst discrete section 201 and the second discrete section 202 rotatepast the cutting head 506. As discussed above, the separation plane 200may be advantageously spaced apart from the corner seam 501 such that,accordingly, a cut made by the cutting head 506 is also spaced apartfrom the corner seam 501.

Referring now to FIG. 6, a flowchart of an exemplary method 600 offorming a tube is shown. It should be appreciated that the exemplarymethod 600 may be carried out, for example, by any one or more of thefabrication systems described herein to form any one or more of thestructures described herein. For example, one or more of the steps ofthe exemplary method 600 may be carried out by a processing unit of acontrol system (e.g., the processing unit 420 of the control system 414in FIG. 4).

As shown in step 602, the exemplary method 600 may include moving amaterial in a feed direction into a curving device. For example, thematerial may be moved substantially continuously in the feed direction,which may be useful for achieving higher throughput than otherwiseachievable through a process requiring periodic interruption in thesupply of material. As used herein, substantially continuous movement ofthe material shall be understood to include movement of the material ata rate that may fluctuate (e.g., according to normal variations in themovement of material using drive rolls or other similar feeding systems)but may remain nonzero throughout the process of forming the tube.

The material moved through the curving device may be any one or more ofthe materials described herein. Thus, for example, the material may bethe material 300 (FIG. 3). Accordingly, the material moved into thecurving device may be a planar strip of material—more specifically, aplanar strip of metal (e.g., steel)—that is curved into one or morecylinders as the material moves through the curving device.

In general, the material moved into the curving device may have a firstdiscrete section abutting a second discrete section along a separationplane intersecting the material. Continuing with this example, the firstdiscrete section and the second discrete section may have the samethickness at the separation plane and each may have a varying thicknessin the feed direction. The respective variations in thickness of thefirst discrete section and the second discrete section in respectivedirections away from the separation plane may include step-wise changesin thickness (such as may be achievable with step-wise changes inmaterial thickness of substantially uniform sheets coupled to oneanother to form the material). Further or instead, the respectivevariations in thickness of the first discrete section and the seconddiscrete section in respective directions away from the separation planemay include substantially continuous changes (e.g., achieved throughmachining) in thickness along at least a portion of each section.

The variations in thickness of the first discrete section and the seconddiscrete section in the respective directions away from the separationplane may have any one or more of various different profiles suitablefor forming cylinders according to a production order producing littleor no scrap in transitions between the cylinders being formed. Forexample, a variation in thickness of the first discrete section may besymmetrically mirrored about the separation plane by a variation in thethickness of the second discrete section. Further, or instead, at leasta portion of the first discrete section may have a monotonicallychanging thickness along the feed direction, and at least a portion ofthe second discrete section may have a monotonically changing thicknessalong the feed direction. For example, the thickness of one of the atleast one portion of the first discrete section and at the at least oneportion of the second discrete section may increase in the feeddirection. In such instances, the thickness of the other one of the atleast one portion of the first discrete section and the at least oneportion of the second discrete section may decrease in the feeddirection.

In certain implementations, the material may include a plurality ofsheets secured to one another in a direction intersecting the feeddirection of the material into the curving device (e.g., alongcross-seams, such as the cross-seams 301 described above with respect toFIG. 3). Along the first discrete section of the material, at least oneof the sheets may have a different thickness than at least one othersheet, thus forming the variation in thickness of the first discretesection. The variation in thickness of the second discrete section maybe similarly defined by variations in thickness of the sheets formingthe second discrete section. The separation plane may advantageouslyintersect only a single sheet of the plurality of sheets such thatthickness of the first discrete section matches thickness of the seconddiscrete section along the separation plane. In certain instances, theseparation plane may bisect the single sheet of the plurality of sheets.Further, or instead, the intersected sheet (or, in some cases, thesubstantially bisected sheet) may be longer than at least one adjacentsheet in the plurality of sheets. Such an increase in length may also orinstead be useful for reducing the likelihood of severing along or nearthe cross seams.

As shown in step 604, the exemplary method 600 may include, as thematerial intersected by the separation plane moves through the curvingdevice, forming the material into a first cylinder having a spiral seamintersected by the separation plane. In general, the formation of thematerial into the first cylinder includes bending the material accordingto any one or more of the curving techniques described herein and, thus,may include moving the material through a triple roll arranged to curvethe material. Further, or instead, moving the material through thecurving device may include bending a first longitudinal edge of thematerial adjacent to a second longitudinal edge of the material, withthe resulting adjacent edges forming the spiral seam. More specifically,forming the material into the first cylinder may include bending a firstedge of the first discrete section adjacent to a second edge of thesecond discrete section at the intersection of the separation plane andthe spiral seam. That is, the separation plane separating the firstdiscrete portion from the second discrete portion may intersect thespiral seam. Further, or instead, the separation plane may beperpendicular to a longitudinal axis defined by the first cylinder beingformed. Such a perpendicular orientation may produce an end cutsubstantially perpendicular to the longitudinal axis defined by thefirst cylinder, such as may be required in the final application (e.g.,a wind tower may require an end cut perpendicular to the longitudinalaxis of the cylinder to facilitate vertical orientation of the cylinderin the final application). Such a perpendicular orientation may beadvantageous for facilitating severing the first cylinder from theremainder of the material (e.g., rotation of the curved material aboutthe longitudinal axis of the cylinder and relative to a cutting head maybe incorporated into a severing process as described herein).

As shown in step 606, the exemplary method 600 may include joining thefirst discrete section to itself and to the second discrete sectionalong the spiral seam. As part of a continuous process of forming thetubes, such joining may include continuously joining material along thespiral. More generally, joining the first discrete section to itself andto the second discrete section along the spiral seam may be carried outaccording to any one or more of the joining methods described hereinand, thus, may include welding (e.g., continuously welding) the materialin instances in which the material is suitable for welding. Further, orinstead, in implementations in which the material is formed by joiningsheets together along cross-seams, joining the first discrete section toitself and to the second discrete state may include forming corner seamsof the material along the spiral seam. Continuing with this example, itmay be desirable to position the separation plane such that theintersection of the separation plane and the spiral is spaced apart fromthe corner seams to reduce the likelihood that severing along theseparation plane will result in the formation of undesirable fatiguelocations along one or more of the tubes being formed.

As shown in step 608, the exemplary method 600 may include severing thefirst discrete section (formed as the first cylinder) from the seconddiscrete section along the separation plane intersecting the spiral seamalong a position at which the first discrete section is joined to thesecond discrete section. More specifically, the first discrete sectionmay be severed from the second discrete section as a segment of thesecond discrete section is in the curving device. That is, given thatthe first discrete section corresponds to the first cylinder at the timeof severing, the first cylinder may be severed from the second discretesection as the segment of the second discrete section is in the curvingdevice, which may be particularly useful for continuously formingcylinders according to the exemplary method 600.

Such severing may be achieved according to any one or more of thesevering techniques described herein and, in general, may includecutting the material along an entire circumference of the first cylinderto separate the first cylinder from a second cylinder being formed asthe second discrete section moves through the curving device. That is,the separation plane may bound a trailing edge of the first cylinder anda leading edge of the second cylinder and, accordingly, severing alongthe separation plane may form the trailing edge of the first cylinderand the leading edge of the second cylinder. Thus, to facilitateachieving suitable dimensional tolerance in the formation of the firstcylinder and the second cylinder, each of the first cylinder and theportion of the second cylinder formed at the time of severing may remainundeformed as the first discrete section is severed from the seconddiscrete section.

As shown in step 610, the exemplary method 600 may, optionally, includeforming the second discrete section into the second cylinder. As shouldbe generally understood, the steps for forming the second cylinder maybe identical or at least substantially similar to the steps associatedwith forming the first discrete section into the first cylinder.Likewise, the second cylinder may be joined and severed in stepsanalogous to those described above with respect to the first cylinder.More generally, the steps of the exemplary method 600 may be repeated asnecessary to form a plurality of cylinders associated with a productionorder. Thus, for example, the steps of the exemplary method 600 may berepeated as necessary to form a third cylinder, a fourth cylinder, afifth cylinder, etc.

While certain embodiments have been described, other embodiments areadditionally or alternatively possible.

For example, while the special case of producing substantially identicalinstances of a cylinder has been described, it should be appreciated themethods of the present disclosure may be carried out more generally toproduce cylinders of different sizes. That is, the permissiblecombination of sizes that may be formed according to the methodsdisclosed herein are generally governed by the three criteria describedabove with respect the production order “P” shown in FIG. 2. Namely, thedevices and systems of the present disclosure may carry out any one ormore of the methods described herein to form any combination of cylindersizes provided that the following criteria are met at each separationplane delineating adjacent cylinders in a production order: 1) eachcylinder has a matching taper at the separation plane; 2) each cylinderhas the same radius of curvature at the separation plane; and 3) eachcylinder has a matching thickness at the separation plane. The firstcriterion should be generally understood to be met by the fabrication ofcylinders. Thus, the second and third criteria may generally govern apermissible production order of cylinders of varying sizes.

Referring now to FIGS. 7 and 8, cylinders 101 and 102 are cylinders ofvarying size that may be formed according to the production order “PP”.Elements in FIG. 8 denoted with primed (′) element numbers should beunderstood to be substantially analogous to corresponding elements withunprimed numbers in FIG. 2. Thus, for the sake of efficient and cleardescription, these primed element numbers are not described again,except to highlight any differences with respect to correspondingunprimed elements in FIG. 2. Accordingly, unless otherwise specified ormade clear from the context, a separation plane 200′ in FIG. 8 should beunderstood to be analogous to the separation plane 200 in FIG. 2, unlessotherwise specified or made clear from the context.

In general, the cylinders 101 and 102 may be formed from a plurality ofsheets. In particular, the cylinder 101 may be formed from sheets t1,t2, t3, t4, t5, t6 and, thus, may be understood to be substantiallysimilar to the cylinder 100 (FIG. 1), unless otherwise specified or madeclear from the context. The cylinder 102 may be longer than the cylinder101 and may be formed of sheets t6, t7, t8, t9, t10, t11, t12, t13, t14,t15. Further, or instead, the thickness profile of the cylinder 101 maydiffer from a thickness profile of the cylinder 102, provided that thethickness profiles along the first discrete section 201′ and the seconddiscrete section 202′ match at the separation planes 200′. The cylinders101 and 102 may be formed in a substantially continuous process in whichthe sheets t1, t2, t3, . . . t15 are fed into a fabrication system(e.g., the fabrication system 400 in FIG. 4) according to an order basedon the production order PP.

The above systems, devices, methods, processes, and the like may berealized in hardware, software, or any combination of these suitable forthe control, data acquisition, and data processing described herein.This includes realization in one or more microprocessors,microcontrollers, embedded microcontrollers, programmable digital signalprocessors or other programmable devices or processing circuitry, alongwith internal and/or external memory. This may also, or instead, includeone or more application specific integrated circuits, programmable gatearrays, programmable array logic components, or any other device ordevices that may be configured to process electronic signals. It willfurther be appreciated that a realization of the processes or devicesdescribed above may include computer-executable code created using astructured programming language such as C, an object orientedprogramming language such as C++, or any other high-level or low-levelprogramming language (including assembly languages, hardware descriptionlanguages, and database programming languages and technologies) that maybe stored, compiled or interpreted to run on one of the above devices,as well as heterogeneous combinations of processors, processorarchitectures, or combinations of different hardware and software. Atthe same time, processing may be distributed across devices such as thevarious systems described above, or all of the functionality may beintegrated into a dedicated, standalone device. All such permutationsand combinations are intended to fall within the scope of the presentdisclosure.

Embodiments disclosed herein may include computer program productscomprising computer-executable code or computer-usable code that, whenexecuting on one or more computing devices, performs any and/or all ofthe steps of the control systems described above. The code may be storedin a non-transitory fashion in a computer memory, which may be a memoryfrom which the program executes (such as random access memory associatedwith a processor), or a storage device such as a disk drive, flashmemory or any other optical, electromagnetic, magnetic, infrared orother device or combination of devices. In another aspect, any of thecontrol systems described above may be embodied in any suitabletransmission or propagation medium carrying computer-executable codeand/or any inputs or outputs from same.

The method steps of the implementations described herein are intended toinclude any suitable method of causing such method steps to beperformed, consistent with the patentability of the following claims,unless a different meaning is expressly provided or otherwise clear fromthe context. So, for example, performing the step of X includes anysuitable method for causing another party such as a remote user, aremote processing resource (e.g., a server or cloud computer) or amachine to perform the step of X. Similarly, performing steps X, Y and Zmay include any method of directing or controlling any combination ofsuch other individuals or resources to perform steps X, Y and Z toobtain the benefit of such steps. Thus, method steps of theimplementations described herein are intended to include any suitablemethod of causing one or more other parties or entities to perform thesteps, consistent with the patentability of the following claims, unlessa different meaning is expressly provided or otherwise clear from thecontext. Such parties or entities need not be under the direction orcontrol of any other party or entity, and need not be located within aparticular jurisdiction.

It will be appreciated that the methods and systems described above areset forth by way of example and not of limitation. Numerous variations,additions, omissions, and other modifications will be apparent to one ofordinary skill in the art. In addition, the order or presentation ofmethod steps in the description and drawings above is not intended torequire this order of performing the recited steps unless a particularorder is expressly required or otherwise clear from the context. Thus,while particular embodiments have been shown and described, it will beapparent to those skilled in the art that various changes andmodifications in form and details may be made therein without departingfrom the spirit and scope of this disclosure and are intended to form apart of the invention as defined by the following claims, which are tobe interpreted in the broadest sense allowable by law.

What is claimed is:
 1. A tube comprising: a first discrete section of amaterial, the first discrete section shaped as a first cylinder, thefirst discrete section including a spiral seam extending along the firstcylinder; and a second discrete section of the material, the seconddiscrete section abutting and joined to the first discrete section alonga separation plane intersecting the material, the spiral seamintersecting the separation plane and extending along the seconddiscrete section, the first discrete section and the second discretesection each having the same thickness at the separation plane, and thefirst discrete section and the second discrete section each having avarying thickness in a respective direction away from the separationplane.
 2. The tube of claim 1, wherein the separation plane intersects alongitudinal axis defined by the first cylinder.
 3. The tube of claim 2,wherein the separation plane is perpendicular to the longitudinal axisdefined by the first cylinder.
 4. The tube of claim 1, wherein thedirection of varying thickness of the first discrete section is oppositethe direction of varying thickness of the second discrete section. 5.The tube of claim 1, wherein the direction of varying thickness of thefirst discrete section is along a longitudinal axis defined by the firstcylinder.
 6. The tube of claim 1, wherein the second discrete section ofthe material is shaped as at least one portion of a second cylinder. 7.The tube of claim 6, wherein first cylinder and the at least one portionof the second cylinder abut one another along the separation plane. 8.The tube of claim 1, wherein the variation in thickness of the firstdiscrete section in a direction away from the separation plane ismonotonic.
 9. The tube of claim 8, wherein the variation in thickness ofthe second discrete section in the direction away from the separationplane is monotonic.
 10. The tube of claim 1, wherein the variation inthickness of the first discrete section and the variation in thicknessof the second discrete section are symmetrically mirrored relative toone another about the separation plane.
 11. The tube of claim 1, whereinthe variation in thickness of the first discrete section is includes astep-wise change in material thickness in a direction away from theseparation plane.
 12. The tube of claim 1, wherein a radius of curvatureof the first discrete section matches a radius of curvature of thesecond discrete section at the separation plane.
 13. The tube of claim1, wherein the first cylinder includes one or more corner welds alongthe spiral seam.
 14. The tube of claim 13, wherein the separation planeintersects the spiral seam away from the one or more corner welds alongthe spiral seam.
 15. The tube of claim 1, wherein the first cylinder issubstantially a right circular cylinder.
 16. The tube of claim 1,wherein the material is metal.
 17. The tube of claim 16, wherein thespiral seam includes a weld.